Real Time Bus Information: How do the times go backwards?

veryangryman

Always wondered this...other day my 25a said 2 mins, followed by 3 mins to the next bus. Could they be going backwards? Surely it decremements the remaining time based on how near the bus is getting?

Outkast_IRE

veryangryman wrote: »

Always wondered this...other day my 25a said 2 mins, followed by 3 mins to the next bus. Could they be going backwards? Surely it decremements the remaining time based on how near the bus is getting?

It can adjust based on the buses progress. If the bus runs into heavy traffic it can increase to provide a more accurate indication of when to expect the bus.

Or like my local one, the bus can simply not show up and the clock resets back to when the next bus is due.

Kh1993

Also, if you're anywhere near a terminus real time info isn't anything like 'real time'. It counts down to Due based on the timetable, can disappear and you're left wondering (1) has it vanished into thin air with no warning, or (2) the driver just hasn't switched bus on - when they do it'll reappear.

suicide_circus

They're really just a vague indicator of when the bus might show up.

5 nom

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Etc

Wanderer78

Technically, how is the time measured?

KD345

Wanderer78 wrote: »

Technically, how is the time measured?

Each bus journey is logged into the system based on the timetable. This forms the original time displayed on screen and app. Once that bus journey goes live (driver logs into the system from their cab) their real time location replaces the scheduled time. Each route has a calculated time between stops based on route, time of day and day of week. As the bus progresses along its route it pings a GPS signal every 30 seconds which is fed into the system and sent to screens and the app.

If the bus is running ahead of its usual journey time (light traffic, no passengers at stops etc.) then you'll notice the minutes count down quicker as it recalculates its expected arrival time. If suddenly, something delays the bus (accident, passenger, traffic) then the system will revise its time, which is why you'll occasionally see it count up instead of down.

This can confuse passengers, but really it's just the system reflecting 'real time' information. It's just like you calling a friend to say you'll be with them in 3 minutes, but then something delays you unexpectedly and it takes you 4 minutes.

Journeys can be altered by the controller to delete, alter and curtail bus journeys. If a bus is delayed reaching its terminus that may mean a delayed departure of its return journey and this can be adjusted in advance.

Where you'll sometimes see a bus displaying a time e.g. "2 min" for a period of time, that usually means the bus hasn't been held up unexpectedly but is 2 minutes from your stop.

The system cannot display non-timetabled buses or extra departures as they officially don't exist on the timetable and therefore have not been input into the system.

The RTPI is not perfect but considering the traffic and road conditions in the city I think it does pretty well. There are lots of improvements which could be made but we have seen the app improve over time and I'm sure that will continue as technology advances.

sharper

KD345 wrote: »

The RTPI is not perfect but considering the traffic and road conditions in the city I think it does pretty well. There are lots of improvements which could be made but we have seen the app improve over time and I'm sure that will continue as technology advances.

We live in a world where many people have a smartphone so we're not limited to just what the physical displays at the stops can show. If they would publish where the bus actually is, whether it's a "real" position or just the timetabled position and actully update it all when a bus isn't running for "operational reasons" then it would be far more useful.

If you ever check twitter you'll see daily complaints about particular services not tracking. These never seem to be fixed and preseumably it's just a matter of them inputting the timetable correctly.

n97 mini

Kh1993 wrote: »

Also, if you're anywhere near a terminus real time info isn't anything like 'real time'. It counts down to Due based on the timetable, can disappear and you're left wondering (1) has it vanished into thin air with no warning, or (2) the driver just hasn't switched bus on - when they do it'll reappear.

I live near a terminus and the departure time reflects if the bus is held up coming to the terminus. The system just needs to be programmed (and I'm sure it is in my case) as if it's one single long route with the terminus in the middle.

Having said that buses departing from the city centre terminus can be hit and miss. Some do seem to count down based on the timetable, and then disappear.

My biggest gripe with the RTPI is that it doesn't show cancelled services. Instead it shows the timetabled bus, or nothing at all. In the latter case you don't know if it's cancelled or the driver just hasn't switched on the system.

bk

KD345 wrote: »

The system cannot display non-timetabled buses or extra departures as they officially don't exist on the timetable and therefore have not been input into the system.

Great explanation on how the system works. But the above part seems strange. It should technically be relatively easy for the system to display such buses, once the driver has input the route number and the system has connected. It should just use the GPS location of the bus to give arrival estimates.

ArmaniJeanss

bk wrote: »

Great explanation on how the system works. But the above part seems strange. It should technically be relatively easy for the system to display such buses, once the driver has input the route number and the system has connected. It should just use the GPS location of the bus to give arrival estimates.

Might be an issue that buses (of the same number) take different routes at different times of the day.
So for example the system knows that the 16.10, 16.30 and 17.00 38s go through Ballycoolin, whereas the 15:50 and 17.20 onwards don't.
The RTPI can cater for this only if it knows which timetabled departure a bus is, a random extra 38 put on the route can't have RTPI because the system doesn't know where its going.

I'm not sure how many routes have such a quirk though.

seamus

Still though no technical reason why it's not possible - the system is aware of the two different routes. So when the driver tells the bus it's a 38, the system asks him whether it's a 38 via Ballycoolin, or a normal 38.

These seem like minor gripes to be fair, though it would be nice to see some small enhancements, such as notes on the board which indicate that an ETA is based on the timetable and not on the RTI, cancellations shown on the board for say ten minutes after they happen, and a way for drivers to indicate they've been caught in a serious delay, so although they're physically 4 minutes away, they may logistically not arrive for quite a while.

LXFlyer

bk wrote: »

Great explanation on how the system works. But the above part seems strange. It should technically be relatively easy for the system to display such buses, once the driver has input the route number and the system has connected. It should just use the GPS location of the bus to give arrival estimates.

Every single departure has an individual timetable based on the time of day that reflects the normal traffic conditions at that time - the real time system reads where the bus is and then applies the time taken to each stop per that timetable based on the current location.

The driver inputs his departure time and route to read the correct timetable to generate the predictive times at stops. That's how the system can differentiate between buses on certain routes that have route variations.

An extra untimetabled service won't have predictive times to read from.

Look at the "Find a timetable" section on www.a-b.ie and select a DB route to see a sample control timetable. Bear in mind though that the system uses the planned time taken between stops from that timetable once the bus is live and applies them to where the bus currently is rather than the actual times shown.

Outkast_IRE

sharper wrote: »

We live in a world where many people have a smartphone so we're not limited to just what the physical displays at the stops can show. If they would publish where the bus actually is, whether it's a "real" position or just the timetabled position and actully update it all when a bus isn't running for "operational reasons" then it would be far more useful.

If you ever check twitter you'll see daily complaints about particular services not tracking. These never seem to be fixed and preseumably it's just a matter of them inputting the timetable correctly.

On the bus eireann real time website you can check where the bus is actually now in almost real time you just need to go to the arrivals for your bus stop and you can see its location update
on mobile now so can't post link but I use it almost every day

XPS_Zero

We take this for granted, like Luas, but I remember what it was like before it. It was utter hell, because at that time we didn't have smartphone apps either.

Before RT and Smartphones and Network Direct, it wasn't unusual to wait an hour or longer for some bus routes (COUGH 84 COUGH). We forget how bad it was before. Before 1997 this country was a radically different place. We hear complaints about how the disabled set up works on public transport, and I agree it could improve, but before 2004 there was NO provision at all, it was "fu-k you" if your'e disabled, sort your own self out. No lifts, no kneeling busses, no ultrawide doors, no ultrawide ticket gates, none of that, that wasn't an obvious drop from the sky thing it had to be planned and done because there was nothing there before.

We (rightly) moan on here about how Transport 21 came to a screeching halt before some of the more important aspects like DU, MN and Luas line F were implemented but we should not loose sight of how much things have improved either.

seamus

Indeed, I imagine those of us who remember public transport before 2004 would have a right old chuckle hearing teenagers complain about RTPI being a little inaccurate, the odd bus going past because it's full and having to wait at bus stops without shelters.

Stephen15

Often when I use a bus particularly on a weekend its 10 mins and and then all of a sudden its 55 mins how the hell does that happen?

Cookie_Monster

KD345 wrote: »

Each bus journey is logged into the system based on the timetable. This forms the original time displayed on screen and app. Once that bus journey goes live (driver logs into the system from their cab) their real time location replaces the scheduled time. Each route has a calculated time between stops based on route, time of day and day of week. As the bus progresses along its route it pings a GPS signal every 30 seconds which is fed into the system and sent to screens and the app.

really? How come my dirt cheap cycling GPS or phone can do it real time but DB only every 30 seconds, that's a huge lag!

trellheim

Standard SA ( Situational Awareness ) pinging is every 30 seconds if I recall.

Your phone GPS does not ping its location continuously to a remote location , different thing entirely.

n97 mini

Cookie_Monster wrote: »

really? How come my dirt cheap cycling GPS or phone can do it real time but DB only every 30 seconds, that's a huge lag!

If you were paying for 1000 mobile phones you'd probably be happy to cut a few corners!

cython

trellheim wrote: »

Standard SA ( Situational Awareness ) pinging is every 30 seconds if I recall.

Your phone GPS does not ping its location continuously to a remote location , different thing entirely.

All depends on your opinions of Google location services, etc.

In all seriousness though, some apps on phones do exactly that, in particular sports tracking ones like Strava/Endomondo, and similarly Garmin Edge bike computers that can be paired with a phone via bluetooth send a location more frequently than every 30 secs. However the other question that occurs to me is the utility of providing information more frequently than every 30 secs if there is a time lag associated with plugging the data into a calculation, and propagating the extrapolated data - no point in pinging every second if the downstream system can only make use of data every 15 seconds, for example, due to the turnaround time of processing it.

trellheim

Fair point ! I was discussing it more in the line of battery drain , turning continuous GPS pinging on will drain the battery sharpish !

Stephen15

XPS_Zero wrote: »

We take this for granted, like Luas, but I remember what it was like before it. It was utter hell, because at that time we didn't have smartphone apps either.

Before RT and Smartphones and Network Direct, it wasn't unusual to wait an hour or longer for some bus routes (COUGH 84 COUGH). We forget how bad it was before. Before 1997 this country was a radically different place. We hear complaints about how the disabled set up works on public transport, and I agree it could improve, but before 2004 there was NO provision at all, it was "fu-k you" if your'e disabled, sort your own self out. No lifts, no kneeling busses, no ultrawide doors, no ultrawide ticket gates, none of that, that wasn't an obvious drop from the sky thing it had to be planned and done because there was nothing there before.

Back in the good old days when the service between the CC and Bray was more or less hourly between the makey up timetable 45 and the in-frequent 84. Ah you got me nostalgic there

LXFlyer

Deedsie wrote: »

Really good informative post. Thanks

Why can the controller not add in non timetabled buses?

The x12 expressway bus is late every single day. Should they not just alter the times it departs Dublin airport to 20 minutes earlier so that the rest of the journey does not have such a knock on effect? The expressway timetable doesnt seem to take rush hour traffic into account

Each individual departure needs to have predictive times for it set up in the system - given that a non-timetabled extra bus may/may not operate, and its departure time will fluctuate from one day to the next depending upon demand, it's not really feasible to include them.


The X12, 20/X20 and indeed other operator's schedules should of course be recast to reflect actual journey times. Departing earlier may not be possible depending upon when the bus arrives at Dublin Airport.

LXFlyer

Deedsie wrote: »

I accept that, but surely having an unachievable timetable is not exactly providing a good service for commuters. If they say the X12 will be at X at 15:40 surely there should be a requirement for them to be there within +/- 5 mins.

I really dislike having to drive to work but it is very hard for people to rely on these buses to get to and from work.

Eh, I just said that the X12 timetable should be recast to reflect actual journey times. That may mean that the timetable has later intermediate times than at present but which reflects reality.

thomasj

It happens a lot that standing at the stop after Aston quay and the 39A could be showing 1 minute for up to 10 minutes.

Sounds like its down to the time at lights to get to the stop, driver handover and numbers boarding and getting stuck along the south quays to get to that next stop.

Ben D Bus

veryangryman wrote: »

Always wondered this...other day my 25a said 2 mins, followed by 3 mins to the next bus. Could they be going backwards? Surely it decremements the remaining time based on how near the bus is getting?

It's kind of like how everyone does it.

When you're leaving the house to go somewhere you go regularly and you think to yourself "I'll be there in 10 minutes".

All goes well for the first 5 minutes and you think "I'll be there in 5 minutes".

Then you turn a corner and see there's an unusually long line of slow moving traffic. You mentally adjust and say to yourself "I might actually be 6 or 7 minutes away".

Not complicated.